Low voltage ride through ability is becoming one of the essential features of large grid-connected wind gen-erators. When the power grid voltage drop occurs, it is necessary for the wind turbines to maintain connecting and return to normal after the fault is eliminated quickly. The most common method of low voltage through is to increase the crowbar protection module, but the protection operations may generate instantaneous current impact, damaging the ro-tors of generator. This paper analyzes the influences of the input and removal strategy of rotor crowbar protection and action time on doubly-fed induction generator (DFIG). Simulations and analysis are made based on the electromagnetic transient simulation software PSCAD/EMTDC.